What is faster: "old" 6509E with SUP32 and WS-X6148A-GE-45AF or 2960S stack?

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Jul 19th, 2012
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We have a choice for buying at a good price a 6509E with SUP32 and 5 x 48 WS-X6148A-GE-45AF POE modules or a 4 x 2960S ( which then will be connected to existing 2 x 3560G 24 ports (for routing)). Both are (including 3 years maintenance) about the same price. What would be the better choice? According to the specs I read that SUP32 with the specific WS-X6148A boards has about 15 mpps performance with backplane speed of 32 Gbps  whereas 2960S with flexstack has much higher mpps speed (up to 100 mpps as I understand) and much higher backplane speed, however this higher speed will probably not be effective when routing over copper etherchannel 4 Gbps to the existing 3560.

My preference would be the 6509E because of all the features, however not sure if we really need them, so key item is really performance.

What would the better choice be ?

Correct Answer by Joseph W. Doherty about 5 years 3 weeks ago

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It's difficult to answer some of your questions, because as I've already noted, Cisco has NOT well documented how the FlexStack works.


For example, 3750 StackWise is documented (after the release of StackWise+) with putting everything on the ring, i.e. even traffic passing between two ports on the same switch.  StackWise is also documented as the source switch removing traffic from the ring.  StackWise+ changes how it operates in these two cases so it much better leverages its ring bandwidth, but how does FlexStack operate?  I've seen it noted as it operates hop-by-hop, unlike StackWise, but what does this really mean?


When comparing the FlexStack dual 10 gig (duplex) links with the 6500's 16 gig (duplex) bus, does adding stack members effectively increase aggregate bandwidth within the stack vs. the 6500 bus?  Does FlexStack add latency with each stack member and have higher latency vs. the 6500 bus?  Again, I haven't seen this documented, and without knowing, how to we really determine which is likely to perform better in different situations?


It used to be the 2960S was only L2 but it now offers limited L3.  How well does it perform L3 vs. a Sup32?  Once again, I don't recall this being well documented.


Instead of looking at just "performance", you might want to also consider other things such as the Sup32 is now EOL.  The 6500 requires a 2nd Sup for sup redundancy (while redundancy is inherent with the FlexStack).  How do service contracts compare in cost?

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Leo Laohoo Thu, 07/19/2012 - 23:46
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2960S has a backplane speed of 10 Gbps (full duplex).

joelvanpraag Fri, 07/20/2012 - 00:00
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Hi leolaohoo, thanks !

When I look at http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps6406/product_data_sheet0900aecd80322c0c.html
I see now indeed that the flexstack speed is 20 Gbps. I was previous wrongly looking at the switching speed of

176 Gbps, but this applies only within the switch itself and not between stack members. So I guess 6509E will give much better performance then right?

Side question: How come you say 10 Gbps where docs say flexstack delivers 20 Gbps?

Leo Laohoo Fri, 07/20/2012 - 00:52
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How come you say 10 Gbps where docs say flexstack delivers 20 Gbps?

Made you blink, didn't I?


The value of "20 Gbps" is in the language of "Market-ology" and expressed in HALF duplex.


10 Gbps is expressed in FULL duplex.


Besides, who nowadays is buying Sup32.  Cisco will be announcing the End-of-Sale of the Sup32 maybe before the end of 2012.


Before you make a decision, can you also compare the price with, say, a 4500R+E with Sup7E?

joelvanpraag Fri, 07/20/2012 - 01:41
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Hi Leolaohoo, aha, that clears things!

So just to summarise:  even with the old SUP32 the 6509E with 5 x 48 G will outperform 5 x 2960S ?


About choosing for SUP32, this is because the price is good : we can get a 6509E with SUP32 box for approx. the same price per port as 2960S with flexstack. If we would put new SUP in there, the price will be too high.

Just one more question about this issue: the box only has 1 SUP32 so for redundancy we will add another SUP. Can you then add another SUP of another (faster) type and is this useful ?

Many thanks!

Joseph W. Doherty Fri, 07/20/2012 - 11:44
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First you might want to be aware the sup32 is no longer available new.  (I understand the factory that produced it burned down, and since it was already getting near a planned EOL, Cisco decided to just have it go EOL earlier than planned.)


As to comparing the 6500/sup32/6148 with 2960S stack (incidentally you can only stack 4 units), performance will vary very much depending on usage.


For the 6500, most everything rides across the 32 Gbps (duplex) bus, and sup32 (as you noted is rated at 15 Mpps, although that's independent of frame size).  (NB: 15 Mpps equal about 10 Gbps, half duplex, @64 byte.)


The 2960S has, as you also note, have much higher PPS and bandwith within a single device, but bandwidth on the stack is dual 10 Gbps (duplex) and Cisco, I don't believe, has well documented how the 2960S stack works, although it seems inferior to 3750 StackWise or StackWise+.


So which is "better"?  Again, really much depends on expected usage.

Leo Laohoo Sat, 07/21/2012 - 17:32
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So just to summarise:  even with the old SUP32 the 6509E with 5 x 48 G will outperform 5 x 2960S ?

You can't stack five (or more) 2960S.  You can only stack up to four.


If you have cost issues, think about the 4500R+E with Sup7E.

joelvanpraag Sun, 07/22/2012 - 04:12
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Hello, Thank you for all your comments, but I still not have the clear answer. I understand now my question is not really 100 % comparable as you can only stack up to 4 x 2960S, however, then let me amend it a little:

- Assume we have 4 x 2960S compared with 6509E with SUP32 and 4 x 48G

- Cost is not an issue, I Mean, I have a special unique deal where I pay same amount for 6509E with SUP32 and 4 x 48G as for the 4 x 2960S. Looking at another (eg 4500) is not an option, as this is more expensive then stacked 2960S.

- for the 2960S configuration there is a connection to a 3560G using a 4 Gig etherchannel, for L3 traffic


So we have different types of traffic:

- L2 traffic within same 2960S switch

- L2 traffic crossing the 2960S stack

- L3 traffic for 2960S (ie going to 3560):

- L2 traffic within 6509E

- L3 traffic within 6509E


All servers are in a separate vlan from the clients, so the essential traffic will mostly be L3 traffic, I think about 80 %.


Now I would like to put figures for performance from 1 to 10, with 10 being the fastest. Is this doable? So for example:

- L2 traffic within same 2960S switch : 10

- L2 traffic crossing the 2960S stack : 4

- L3 traffic for 2960S (ie going to 3560): 2 

- L2 traffic within 6509E : 4

- L3 traffic within 6509E : 4


Is this correct?


Thanks for all your help!

Correct Answer
Joseph W. Doherty Sun, 07/22/2012 - 05:14
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The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.


Liability Disclaimer


In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.


Posting


It's difficult to answer some of your questions, because as I've already noted, Cisco has NOT well documented how the FlexStack works.


For example, 3750 StackWise is documented (after the release of StackWise+) with putting everything on the ring, i.e. even traffic passing between two ports on the same switch.  StackWise is also documented as the source switch removing traffic from the ring.  StackWise+ changes how it operates in these two cases so it much better leverages its ring bandwidth, but how does FlexStack operate?  I've seen it noted as it operates hop-by-hop, unlike StackWise, but what does this really mean?


When comparing the FlexStack dual 10 gig (duplex) links with the 6500's 16 gig (duplex) bus, does adding stack members effectively increase aggregate bandwidth within the stack vs. the 6500 bus?  Does FlexStack add latency with each stack member and have higher latency vs. the 6500 bus?  Again, I haven't seen this documented, and without knowing, how to we really determine which is likely to perform better in different situations?


It used to be the 2960S was only L2 but it now offers limited L3.  How well does it perform L3 vs. a Sup32?  Once again, I don't recall this being well documented.


Instead of looking at just "performance", you might want to also consider other things such as the Sup32 is now EOL.  The 6500 requires a 2nd Sup for sup redundancy (while redundancy is inherent with the FlexStack).  How do service contracts compare in cost?

joelvanpraag Sun, 07/29/2012 - 17:09
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Ok, guys, understand that some vital information simply is not available. As I already said, it is a special deal, so its not what it looks like. Maintenance indeed is more expensive for 6509E, but total price for coming 3 years would be the same. Thanks for your help. Not sure how the rating works here (1st time I used this forum). I cannot mark an answer as "correct", but can assign rating to answers? How do I do that?

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